Day 1012

Thursday.


1511.07872
Hydrostatic and Caustic mass profiles of galaxy clusters
Maughan, et al

Compare X-ray and caustic mass profiles for a sample of 16 massive galaxy clusters.  Assume hydrostatic equilibrium in interpreting the X-ray data, and use large samples of cluster members with redshifts as a basis for applying the caustic technique.  The hydrostatic and caustic masses agree to better than 20% on average across the radial range covered by both techniques (~[0.2-1.25]R_500), and to within 5% on average at R_500.  The mass profiles were measured independently and do not assume a functional form for either technique.  Pervious studies suggest that, at R_500, the hydrostatic and caustic masses are based low and high respectively.  Find that the ratio of hydrostatic to caustic mass at R_500 is 1.05±0.06; thus it is larger than 0.9 at ~3 sigma and the combination of under- and over-estimation of the mass by these two techniques is ~10% at most.  There is no indication of any dependence of the mass ratio on the X-ray morphology of the clusters, indicating that the hydrostatic masses are not strongly systematically affected by the dynamical state of the clusters.  Overall, the results favor a small value of the so-called hydrostatic bias due to non-thermal pressure sources.


1511.07873
Evolution of stellar-to-halo mass ratio at z=0-7 identified by clustering analysis with the Hubble Legacy imaging and early sugary/Hyper Suprime-Cam survey data
Harikane, Ouchi, Ono, More, Saito, Lin, ... et al

Present clustering analysis results from 10,540 LBGs (lyman-break galaxies) at z~4-7 that are identified in a combination of the Hubble legacy deep imaging and the complimentary large-area Subaru/Hyper Suprime-Cam data taken very recently.  Measure angular correlation functions of these LBGs at z~4,5,6, and 7, and fit these measurements using HOD models that provide the estimates of halo masses, M_h~(1-20)e11 Msun.  The M_h estimates agree with those obtained by previous clustering studies in a UV-magnitude vs. M_h plane, and allow to calculate stellar-to-halo mass ratios (SHMRs) of the LBGs.  By comparison with the z~0 SHMR given by SDSS, identify evolution of the SHMR from z~0 to z~4, and z~4 to 7 at the >98% CL.  The SHMR decreases by a factor of ~3 from z~0 to 4, and increase by  factor of ~5 from z~4 to 7. Obtain the baryon conversion efficiency (BCE) of the LBGs at z~4, and find that the BCE increases with increasing DM halo mass.  Finally compare the clustering+HOD estimates with the abundance matching results, and conclude that the M_h estimates of the clustering+HOD analyses agree with those of the simple abundance matching within a factor of 3, and that the agreement is better with those of the sophisticated abundance matching techniques that include sub haloes, incompleteness, and/or star formation rate + stellar mass function evolution.


1511.08083
The Subary FMOS galaxy redshift survey (FastSound).  IV.  New constraint on gravity theory from redshift space distortions at $z\sim 1.4$
Okumura, HIkage, Totani, et al

Measure the z-space correlation function from a spectroscopic sample of 2830 emission line galaxies from FastSound.  The survey, which uses Subaru and covers 1.19<z<1.55, is the first cosmo study at these high redshifts.  Detect clear anisotropy due to RSD both in the correlation function as a function of separations parallel and perpendicular to the LoS and its quadrupole moment.  RSD has been extensively used to test general relativity on cosmo scales at z<1.  Adopting a LCDM cosmo, and using the RSD measurements on scales above 8Mpc/h, obtain the first constraint on the growth rate at the redshift, f(z)sigma8(z)=0.482±0.116 at z~1.4.  This corresponds to 4.2 sigma detection of RSD, after marginalizing over the galaxy bias parameter b(z)sigma8(z).  The constraint is consistent with the prediction of GR f sigma8~0.392 within the 1-sigma confidence level.  Also demonstrate that by combining with the low-z constraints on f sigma8, high-z galaxy surveys like FastSound can be useful to distinguish modified gravity models without relying on CMB anisotropy experiments.